A feature of lightweight components of hybrid design, hereinafter also termed hybrid components, is interlock connectioning of a parent body mostly composed of metal, or of a hollow body which is, if appropriate, of shell type, to a plastics part joined onto or introduced into the same. For the purposes of the present invention, they are also termed lightweight components, and in the case of shell-type components are also termed hollow-chamber lightweight components.
German Offenlegungsschrift 27 50 982 discloses a non-releasable connection involving two or more parts, preferably composed of metal, where the connection is composed of plastic and is produced in a mould which receives the parts to be connected, for example by the injection-moulding process. EP-A 0 370 342 discloses a lightweight component of hybrid design composed of a shell-type parent body, the interior of which has reinforcing ribs securely connected to the parent body, in that the reinforcing ribs are composed of moulded-on plastic and their connection to the parent body is achieved at discrete connection sites by way of perforations in the parent body, where the plastic extends through these and across the area of the perforations, achieving a secure interlock connection.
WO 2002/068257 A1 discloses “integrated structures” composed of metal and plastic, describing a large number of means for connecting the two components securely to one another. WO 2004/071741 A1 discloses the alternative procedure, namely using two operations first to mould the plastic onto the shell-type metal part in such a way that the plastic passes through openings in the metal part and leaves flash material on the other side, with an additional conversion operation then required before this material leads to a secure interlock connection. EP 1 294 552 B1 discloses that, for the production of a hybrid component, it is possible that the metal core has been not completely, but only sectionally, overmoulded by the plastic, to give a secure interlock connection. WO 2004/011315 A1 describes a further variant, in which the metal part provides, both above and below, openings for the secure interlock connection with the overmoulded plastic. WO 2001/38063 A1 describes a composite plastics part composed of at least two sheet-like workpieces of different material, for example plastic and metal, or of different metals or plastics, where the workpieces have been connected to one another in their peripheral region, and the connection is composed of moulded-on thermoplastic. EP 1 223 032 A2 discloses a sheet-type lightweight component of hybrid design. U.S. Pat. No. 6,761,187 B1 discloses a hybrid component in the form of a channel or of a tube with integrated closure composed of a thermoplastic.
It was quickly recognized that lightweight components of hybrid design have excellent suitability wherever high stability, high energy absorption in the event of a crash, and weight saving are important, i.e. in the construction of motor vehicles, for example. EP 0 679 565 B1 discloses the front end of a motor vehicle with at least one rigid transverse bar which extends over most of the length of the front end, with at least one support part which is composed of plastic and which is cast onto the end region of the rigid transverse bar. EP 1 032 526 B1 discloses a load-bearing structure for the front module of a motor vehicle composed of a steel sheet parent body, of an unreinforced amorphous thermoplastic material, of a glass-fibre-reinforced thermoplastic, and also of a rib structure composed of, for example, polyamide. DE 100 53 840 A1 discloses a bumper system or energy-absorber element composed of oppositely arranged metal sheets and connection ribs composed of thermoplastic or thermoset. WO 2001/40009 A1 discloses the use of hybrid technology in brake pedals, clutch pedals or accelerator pedals of motor vehicles. EP 1 211 164 B1 in turn describes the support structure for a motor vehicle radiator arrangement, using a hybrid structure. DE 101 50 061 A1 discloses the upper transverse member in the vehicle front module of hybrid design. U.S. Pat. No. 6,688,680 B1 describes a transverse member of hybrid design in a motor vehicle. EP 1 380 493 A2 gives another example of a front end panel of a motor vehicle, but here the material is not injected around all of the metal part but takes the form of webs bracketing the same. Lightweight components of hybrid design can be used not only for front ends or pedals but also anywhere in the bodywork of a vehicle. Examples of this are provided by DE 100 18 186 B4 for a vehicle door with door casing, EP 1 232 935 A1 for the actual bodywork of a vehicle, and DE 102 21 709 A1 for the load-bearing elements of motor vehicles.
High-flowability thermoplastic compositions are of interest for a wide variety of shaping processes, such as injection-moulding applications. By way of example, thin-walled components in the electrical and electronics industries and in the motor vehicle industry demand low viscosities of the thermoplastic composition, to permit filling of the mould while using minimum filling pressures or clamping forces for the corresponding injection-moulding machinery. This is also relevant to the simultaneous charging of a plurality of injection-moulded components by way of a shared gating system in what are known as multi-cavity moulds. Furthermore, low-viscosity thermoplastic compositions can also often achieve shorter cycle times. Good flowabilities are also specifically very important in the case of highly filled thermoplastic compositions, for example those with glass-fibre content and/or mineral content above 40% by weight.
However, it has now become apparent that the secure metal-plastic composite in the abovementioned applications is primarily achieved via the perforations in the metal and the thermoplastic flowing through the perforations. Disadvantages of this are firstly that additional amounts of thermoplastic are required, thus increasing weight, and that the secure interlock connection is present primarily at the perforations unless additional webs according to EP-A 13 80 493 are provided. A considerable portion of the metal surface is therefore not available at all for secure interlock connection of metal to plastic.
The object of the present invention therefore consisted in producing hollow-chamber lightweight components of hybrid design which firstly have the advantages known from the prior art, e.g. high buckling resistance, high torsional stability, relatively high strength, relatively low weight, and relatively low mould temperatures during production, but where the metal-plastic composite is not achieved by way of individual perforations of, or webs around, the metal, but instead involves the entire contact surface of the geometry of the plastic on the metal surface.